The present invention generally relates to gaming apparatus and, more particularly, to electronic reel-type slot machines having a plurality of reels rotatable about a common axis. In a typical reel-type slot machine, a payoff is made to a player when a winning set of symbols is displayed on the pay line(s) of the machine. To start play, a button is pushed or a handle is pulled to begin rotation of the reels. In early designs, the angular positions of the reels, after they have been stopped, is detected and the appropriate payoff amount, if any, is calculated and paid to the player.
Another approach in modern machines uses a random number generator to select the symbols to be displayed on the pay line(s). For each reel, a stop position is randomly selected to display the symbol corresponding thereto. The payoff is then determined based on a pay table which contains payoff amounts for the various winning symbol combinations. Payoff amounts provided by this approach are limited because there is a fixed limit on the probability of obtaining the maximum payoff which is the reciprocal of the number of reel stop positions per reel raised to the power of the number of reels.
Accordingly, it is desirable to provide new ways to increase reel-type slot machine payoff values while maintaining adequate game revenue for the operator. As the payoff amounts increase, player interest in the game is fostered which leads to maximized game revenue.
One prior art method of increasing payoff values is to employ a "virtual reel". According to this method, a plurality of numbers are assigned to most of the physical reel stop positions and at least one number is assigned to every physical reel stop position. In this way, the chances of winning a larger payoff can be decreased by assigning the stop combinations corresponding to the larger payoffs to fewer numbers.
The present invention provides an alternative method for increasing payoff levels in electronic reel-type slot machines. The payoff amount--not the physical stop positions--is randomly selected from a pre-determined group of payoff values. In particular, two multiplier factors are randomly selected from two separate groups of pre-determined multiplier factors and are then multiplied together to calculate the payoff. The percentage chances of a player winning the highest payoff are controlled because there are fewer large multiplier factors and many small multiplier factors, including the factor 0.
After the amount of the payoff is determined by the random selection and multiplication of the factors, the device displays a set of symbols that correspond to the selected payoff on the pay line. Thus, for example, if a player is entitled to a 20-coin payoff as a result of the random selection of the multiplier factors 2 and 10, the control system then displays a set of symbols on the pay line which correspond to a 20 coin payoff. To do so, the control system randomly selects one of the various reel stop combinations which, according to the pay table, corresponds to a 20 coin payoff.